I need help with these 2 questions

Question

1: Which species has the smaller bond angle, ClO−4 or ClO−3?

2: explain

Answer 1

First of all, it seems that you should have written this as

ClO₄^- and ClO₃^-

The bond angle will be less for ClO₃^- because of its molecular geometry. Referencing VSPER Theory and the configurations for both:

The first is Tetrahedral, or AX₄

The second is Trigonal Pyramidal, or AX₃E

The bond angle is greater for the Tetrahedral molecule, in fact the angle is closer to 109.5 degrees.

The bond angle is between 90 degrees and 109.5 degrees for Trigonal Planar molecules.